[dev] [dvtm] Backfill patch for dvtm

 Attached is another patch for madtty.c at the head of dvtm. This one
adds support for backfilling text from the buffer when a window is
resized with more rows. As an example, let's say you have a window
filled with 70 rows of text, then you resize it to 34 rows. The new
window will push the top 36 rows to the buffer and display just the
bottom 34 rows. Now if you resize it back to 70 rows this patch will pop
36 rows of data out of the buffer and display 70 rows of text again.

Cheers! -Ross